What is a MTA
 

Ok I expect this to be a rather dumb question, but I'm new to linux and more used to Win32 so I have to ask.

What exactly is a MTA? I know it stands for Mail Transport Agent, what I mean is it what handles smtp tasks or does it also handle pop3/imap?

Are programs like Sendmail, Qmail and Postfix MTA's or are they mail server software and you need a 3rd party MTA running as well?

I have a couple of personal domains I'd like to host email for on my debian box and I also have things like a daily chkrootkit cron script that I want to email the results of but can't atm for lack of a MTA.

Yes, your examples of smtp servers are examples of MTAs.

Ok so assuming I installed Sendmail, Postfix or Qmail do they also act as pop3/imap servers or would I need to install third party programs for those?

You would need an additional server for that. I would reccomend Qmail for smtp, courier-imap for imap and qpopper for pop3.